EP0274322B1 - Installation for paint spraying, particularly an installation for the electrostatic spraying of water paint - Google Patents

Description

The invention relates to an installation for spraying coating product such as paint, of the type in which the object to be coated, carried by a conveyor, passes opposite the area of activity of a robot manipulator called hereinafter automaton carrying a projector diffusing the coating product in the form of fine particles, see for example DE-C 3 340 614.

The invention relates more particularly to a new arrangement making it possible both to solve the problem of color changes when the objects which follow one another in front of the automaton must be painted in different colors as well as the problem of the necessary galvanic isolation between the means for dispensing coating products and the spraying means when the paint used has a low resistivity (water-based paint) and when said spraying means incorporate a high-voltage source for the implementation of a electrostatic projection.

A paint spraying installation, in a production unit as large as an automobile manufacturing plant, for example, generally has several very long closed-loop paint distribution circuits (these circuits can cross a whole section from the factory) which establish the link between large paint tanks and the different projection booths. It is therefore necessary to provide such a circuit by color and another circuit of the same kind for the solvent or cleaning product. For obvious safety reasons, these circuits are connected to earth.

Furthermore, in a paint spray booth thus supplied, the objects to be painted, in this case automobile bodies in the example envisaged, are carried by conveyor means passing through the booth in which there is at least one PLC carrying a paint projector and capable of operating in a certain "activity area" inside the cabin. Automatons are commonly used with up to six or seven degrees of freedom or axes, in order to be able to orient the projector at will and make it penetrate into certain fractures of the object to be painted. For simple forms, one can be satisfied with an automaton comprising only three or four degrees of freedom.

The projector can be electrostatic at high speed, pneumatic spraying or hydrostatic. The automaton most often comprises an arm of several segments articulated with respect to each other, this arm possibly being carried by a movable frame along the conveying means. One of the usual problems to solve in this type of installation is that of the color change between two consecutive objects. Indeed, in the automobile industry, in particular, there is no question of painting the bodies in series, according to the color. The most frequent case, on the contrary, is that where the color must practically be changed after each bodywork. This implies being able to implement rinsing and drying cycles of extremely rapid spraying means. For example, a color change can take place every minute or so and the time allowed to carry out all the operations necessary for the color change is of the order of ten seconds.

In known conventional installations, all the coating product distribution circuits are connected, as well as a compressed air circuit and a cleaning product circuit, through controlled isolation valves, to a collector, one branch of which common output is connected to the projector.

To change color, close the valve of the coating product circuit used, a certain time (calculated) before the end of the spraying phase in progress, then open the compressed air valve to push the remaining product towards the projector. Then, the automaton is moved away from the object and oriented towards a recovery receptacle. The cleaning agent valve opens until the manifold and the projector are clean. Then this valve is closed and the compressed air valve opens again to push the cleaning product contained in the collector, towards the recovery receptacle. The opening of the compressed air valve is extended to dry the conduits then, after closing, another valve from another coating product circuit is open to fill the manifold and the conduits until a little coating product of the new color comes out of the projector. The machine is then brought in front of the new object to be coated.

When the installation has only a small number of coating products of different colors, for example three or four, the collector can be placed fairly close to the projector, i.e. on one of the last articulated segments of the automaton, each coating product being supplied by a flexible conduit. On the other hand, when there are too many different coating products (there can be up to twenty) this solution is no longer practicable and the collector must then be placed at a fixed post, its outlet being connected by a single flexible conduit to the projector. When the objects to be coated are bulky and this is the case of automobile bodies, the automata are subject to large displacements parallel to the largest dimension of the objects to be coated, for example five or six meters. In this case, the collector is very far away, for example ten meters, from the projector, which considerably increases the volumes of ducts to be cleaned, therefore the time for the color change sequences. We are often forced to double the supply circuits (collectors, valves, conduits) to use a projected part while the other part undergoes a cleaning and color change cycle. In addition, with each change of color, the quantities of coating product and cleaning product lost are large, of the order of several hundred cubic centimeters.

The installation is further complicated by the fact that, to ensure a constant flow of coating product during the end of the spraying phase where said coating product is pushed by compressed air, it is necessary to provide a regulator for pressure, immediately upstream of the projector, on the coating product circuit. Finally, since the projectors generally have, for a good spraying, outlet openings of small cross section, it is not always possible to eject all the cleaning product through these openings. In fact, for the cleaning of the collector and of the conduits to be efficient and rapid, it is necessary to maintain a turbulent flow, therefore at high speed, therefore at high flow rate. To do this, it is necessary to provide between the pressure regulator and the projector, a purge valve and a purge circuit of large section, ensuring the flow of the cleaning product to the recovery receptacle. In addition, the pressure regulator and the purge valve being in the immediate vicinity of the projector, in an area which may contain a flammable gas mixture and which can be brought to high-voltage when the projector is of the electrostatic type, the control of this device is usually done by compressed air, which requires additional pneumatic lines.

In the case of an electrostatic installation, all these problems relating to color changes are further accentuated when it is desired to use coating products with low resistivity, such as for example water-based paints, while retaining the advantages of an electrostatic projection. In this case, the projector is often brought to a high voltage and it is advisable to avoid the short circuit between this projector and the distribution circuits of coating product connected to the ground. In order for the leakage current to be acceptable with the water-based paints currently in use, insulating conduits with an unacceptable length / section ratio should be used since they lead to very long color change times and loss of coating products. and cleaning product, excessive and unrealistic.

In addition, when the supply conduits for the coating products and the purge circuits are filled with electrically conductive products, the dielectric strength of these conduits must be sufficient, taking into account the high voltage applied. In addition, the quantity of product that they contain represents a relatively large electrical capacity capable of storing energy well above the tolerated limits.

To address the specific problems of color changes with low resistivity coating products, French Patent No. 2,572,662 suggests filling an intermediate reservoir with the amount of paint just necessary for each application. This intermediate tank is stationary, so that each color change requires cleaning not only the tank, but also all the conduits connected to it. In addition, in one of the variants, the re-establishment of the isolation after filling is done by emptying and drying a sufficient portion of conduit, upstream of the intermediate tank. This operation requires a probihitive time each time the color changes.

The invention proposes to solve the problems of color change by considerably simplifying the equipment located between the distribution circuits and the projector, whatever the type of coating product used.

The invention also proposes to reduce the time necessary to carry out a color change, even when the number of different colors is large and the automaton responsible for moving the projector has to move great distances due to the size of the objects to be coated.

In the particular case of electrostatic projection of coating products with low resistivity, the invention further proposes to solve in a particularly simple manner, the problem of insulation between the electrostatic projector and the distribution circuits of coating products, brought to the earth's potential.

In this spirit, the invention mainly relates to an installation for spraying coating products comprising at least one automatic device of the multi-axis type, carrying a product projector, movable opposite a conveyor carrying objects to be coated, circuits for distribution of different coating products, being provided with respective first, similar connection means, grouped together at a fixed station in a zone of activity of said machine, characterized in that said machine carries a tank of coating product, at least during each phase projection, connected to supply said projector and in that this tank communicates with or is provided with first complementary connection means capable of cooperating with said first connection means of any one of the coating product distribution circuits.

Several possible embodiments correspond to the above definition. Thus, the coating product reservoir can be permanently mounted at the end of the arm of the controller. In this case, it suffices for this arm to be able to orient itself, at each color change phase, towards the first aforementioned connection means as well as towards other means of connection of a cleaning product distribution circuit, for clean the tank and fill it with a coating product of another color. It is also possible to use as many tanks as different coating products. In this case, each tank can be separated from the arm of the automaton and "hung up" on its own distribution circuit to be filled there after use. This variant dispenses with the need to clean the tanks. Finally, an intermediate solution may consist in using only two removable reservoirs, one of the reservoirs being carried by the arm of the automaton while the other is connected to the distribution circuits for coating product and cleaning to undergo a color change cycle.

In all cases, it should be noted that the quantity of coating product introduced into the tank for each projection phase does not need to be adjusted according to the dimensions of the object to be painted. The dimensions of the tank only depend on the ability of the machine to support and quickly move a certain mass of coating product. If the automaton cannot support a reservoir of sufficient dimensions to contain all the quantity of coating product necessary to completely paint the object, it is perfectly possible to consider recharging this reservoir one or more times during the idle times of the projection phase. If, on the other hand, the capacity of the reservoir makes it possible to accommodate more coating product than necessary for a spraying phase, the excess quantity is reinjected into the corresponding distribution circuit, at the start of the color change cycle.

• - la figure 1 est une vue schématique d'une installation pendant un cycle de projection de peinture utilisant un automate à plusieurs degrés de liberté équipée des perfectionnements conformes à l'invention;
• - la figure 2 est une vue schématique analogue à la figure 1, montrant la position de l'automate pendant un cycle de changement de couleur;
• - la figure 3 est une vue de dessus de la figure 2;
• - la figure 4 est une vue schématique illustrant une variante de l'invention;
• - la figure 5 est une vue de dessus de la figure 4;
• - la figure 6 est une vue schématique illustrant une autre variante possible conforme à l'invention; et
• - la figure 7 est une vue de dessus de la figure 6;

The invention will be better understood and other advantages of it will appear more clearly in the light of the description which follows, of several paint spraying installations in accordance with its principle, given solely by way of example and made in reference to the accompanying drawings in which:

• - Figure 1 is a schematic view of an installation during a paint spraying cycle using an automaton with several degrees of freedom equipped with the improvements in accordance with the invention;
• - Figure 2 is a schematic view similar to Figure 1, showing the position of the machine during a color change cycle;
• - Figure 3 is a top view of Figure 2;
• - Figure 4 is a schematic view illustrating a variant of the invention;
• - Figure 5 is a top view of Figure 4;
• - Figure 6 is a schematic view illustrating another possible variant according to the invention; and
• - Figure 7 is a top view of Figure 6;

Referring to Figures 1 to 3, there is shown schematically a first embodiment of the invention, in a paint booth 11 crossed by conveyor means 12 circulating objects 13 to be painted (in this case here bodies automobile) near an automaton 14. This automaton is of the mufti-axes type, known per se; it mainly consists of a chassis 15 movable on a guide 16 extending over a certain distance along the conveying means and an arm 18 carried by the chassis, composed of several articulated segments 18a, 1 BQ, 18 _Q one to another. The chassis 15 itself comprises two parts 15a, 15b connected by an articulation with a vertical axis, allowing it to pivot on itself, as seen in the comparison of FIGS. 1 and 2. We define as "zone of activity "of said automaton all the space of the cabin that can be reached by the automaton and more particularly by the last segment 18c of its arm.

In the example, the segment 18c carries the means for spraying the coating product, in this case a projector 20, supplied with compressed air by a flexible duct 21 and according to the invention, a reservoir for coating product 22. S ' it is an electrostatic installation, the automaton may include a high-voltage generator 24 connected to the projection nozzle or to the bowl in the case of a sprayer at high speed of rotation. Conventionally, the high-voltage generator 24 is adjustable at will, that is to say in particular that its output voltage can be reduced to zero at any desired time and restored almost instantaneously under the action of control means. very classic. This possibility of adjusting the high voltage, although banal in itself, is of particular importance in the context of the invention, since the projector is, at each filling and / or cleaning sequence, connected to the distribution network of product connected to ground.

In the example described, the reservoir 22 is permanently mounted on the last segment of the automaton and communicates with the projector 20. If the reservoir is too large to be able to be mounted on the last segment, it can be mounted on the penultimate and connected by a flexible conduit to the projector.

Furthermore, conduits forming part of different distribution circuits, pass through the cabin 11; they are for example fixed along a wall 26 thereof. Thus, in the example shown, there are three paint distribution circuits P1, P2 and P3 (these are paints of different colors), a cleaning product distribution circuit N and a waste evacuation circuit D There is also provided a compressed air supply circuit A to which the conduit 21 is connected, by means of a controlled valve 25. The circuits P1, P2 and P3 are provided with first connection means 28a, respectively, similar, grouped in the activity area of the automaton defined above, that is to say in the vicinity of the wall 26. Each of these first means of connection of any of the circuits P1, P2, P3 is capable of cooperating with first complementary connection means 29a carried by the reservoir 22. In the example of FIGS. 1 to 3, said first connection means of each circuit P1, P2 or P3 are simply constituted, respectively, by a single cunt element nector of the “self-closing ball quick connector” type well known in the art while the first complementary connection means 29 are only constituted by another connector element, of complementary structure, capable of being plugged in tightly to one elements of the connector of circuits P1, P2 or P3. Likewise, the cleaning product distribution circuit N and the waste evacuation circuit D respectively comprise connection means 28Q, 28c, to the reservoir 22, in this case identical to said first connection means of circuits P1 , P2 or P3 since they consist of the same connector elements. All the connection means 28a, 28b, 28c are grouped very close to each other in said activity zone of the automaton.

In addition, a waste recovery receptacle 30 is also located in the activity area, not far from the connection means 28a, 28 _L b and 28s. This receptacle is designed to receive any product (paint or cleaning product) rejected as a jet by the projector 20.

It should be noted that the compressed air line 21 can communicate directly with the reservoir 22 if the automaton is programmed so as never to place the pressurization air supply at a level below the paint outlet, so as to avoid air being directly discharged from the projector when it is facing an object to be painted. A control system, known per se, of the quantity of paint sprayed makes it possible to never completely empty the tank during spraying. It is also possible to use another type of reservoir comprising a piston or a deformable member, arranged to divide the internal space of the reservoir into two chambers, one of the chambers receiving the product and the other being intended to receive air. under pressure. In this case, it is obvious that the first complementary connection means 29a communicate with the chamber receiving the product and that the conduit 21 communicates with the other chamber, in order to push back the piston or the membrane as the evacuation of the product by the projector 20 or by the first complementary connection means 29a.

The operation is as follows. At the end of a projection phase illustrated in FIG. 1 where the valve 25 is open to allow the pressurized air to push the coating product towards the projector 20 where it is sprayed or projected towards the object to be painted , the controller 15 pivots on itself to approach the reservoir 22 of the location of the cabin where the various connection means described above are located. If it is necessary to change the color of the paint, for example switching from the paint dispensed by P1 to the paint dispensed by P2, the machine first connects the reservoir to the circuit P1 so as to reinject the excess of paint or at least most of this excess by controlling the amount repelled to avoid injecting air into this circuit. Then, the automaton puts the reservoir 22 in communication with the cleaning product distribution circuit N, the circuit 21, by virtue of the three-way valve 25 being vented to allow the tank to be filled. When the tank is filled, the automaton connects the tank, still by the same connection means, to the waste evacuation circuit D and the valve 25 is again connected to evacuate the cleaning product in this circuit. The two previous operations are possibly repeated several times, if necessary, until the tank is clean. After which, the machine directs the projector 20 towards the receptacle 30 and compressed air is again injected to drain a small part of the cleaning product through the projector, so as to clean it. Then, the automatic device connects the reservoir 22 to the distribution circuit P2 while the circuit 21, thanks to the valve 25, is again vented to allow the reservoir to be filled with the new paint. After which, the automaton brings the projector 20 back to the receptacle 30 to project a small amount of product therein and thus eliminate the last traces of cleaning product. From this moment, the color change cycle is completed and the automaton can again pivot on itself to paint a new body.

In the case of an electrostatic projection installation, the high voltage is brought to zero before the start of the color change cycle and is not re-established until the end of the cycle. It is clear that during the entire projection period, the high-voltage is perfectly isolated from the various distribution circuits connected to the ground since there is no product conduit between them.

We also appreciate that the equipment carried by the PLC is very simplified. The conventional purge valves and purge circuit are omitted since, during the cleaning of the reservoir 22, pes products are introduced and evacuated essentially by the connection means described above, which have a much larger passage section than that of the projector. 20. The cleaning product is only admitted into the sprayer 20 in very small quantities, only for cleaning the latter. Likewise, a pressure regulator is not necessary since the installation does not include a long pipe in which paint is pushed with pressurized air at the end of the spraying period. Here, the paint is pushed into the tank where there is no variation in pressure losses.

Figures 4 and 4 where the similar elements have the same alphanumeric references, illustrate a variant in which the color change cycle can be very significantly shortened, since it requires no cleaning. In fact, the installation is provided with as many coating product reservoirs 22 ₁ , 22 ₂ , 22 ₃ ... as there are distribution circuits P1, P2, P3 ... These reservoirs are therefore not permanently dismantled second connection means (not shown) carried on the automaton, but not connected thereto, capable of cooperating with second complementary connection means 34a, 34J _B provided on each tank. These connection means are composed from the same connector elements as those used in the first embodiment described. However, the second connection means provided on the automaton consist of two connector elements spaced by a predetermined distance while the second complementary connection means 34a, 34b also consist of two corresponding connector elements spaced by the same distance for adapt to the elements carried by the automaton. Once the reservoir is in place on the automaton, one of the connector elements of the reservoir is in connection with the compressed air while the other is in connection with the projector. Each reservoir may be of the type described above, with a piston or deformable member.

The first aforementioned connection means of each distribution circuit P1, P2 or P3 also consist of two connector elements 28ai, 29a ₂ . These are spaced by a dis predetermined voltage on either side of a restriction 35 connected in series in the corresponding circuit P1, P2 or P3, this circuit being, as usual, of the continuous circulation type in closed loop.

Similarly, said first complementary connection means provided on each tank comprise two other connector elements 29a1, 29a2 spaced the same distance along said tank.

According to an advantageous arrangement, the circuits P1, P2 and P3 have a height variation on either side of the restriction 35. The arrangement is such that the two connector elements 28a1, 28a2 are arranged at different levels, l connector element 28a1 placed at the highest level being downstream of the other connector element, with respect to the direction of circulation of the coating product in the corresponding distribution circuit. In addition, the connector element 28a1 placed downstream is connected to the distribution circuit via a three-way controlled valve 36, the other outlet of which communicates with a discharge circuit 37. The latter is common to all the valves 36. The operation is as follows.

When the automaton has finished painting an object and a change of color is necessary, it comes to "hang up" the reservoir to said first connection means 28ai, 28a2 of the distribution circuit of the corresponding color. Then, the automaton will take the tank connected to another circuit corresponding to the new color. From this moment, the automaton is already ready to paint the next object.

During this time, the tank which has just been "hung up" gradually fills, the corresponding valve 36 being in communication with the discharge circuit 37. Because a slight pressure drop is created in the corresponding distribution circuit by restriction 35, the paint fills the reservoir until a small amount is discharged through the discharge circuit 37. From this moment, the reservoir is full and again ready for use. The valve 36 is then switched and the paint continues to circulate slowly, bypass, in the reservoir, until the automaton again comes to take up the reservoir. The circulation of the paint, maintained in the tank, avoids the sedimentation by gravity of the various constituents thereof. Of course, during any phase of hanging up a tank and taking off from another tank, the high-voltage is brought to zero. We can provide two tanks for each color, to further limit downtime if two consecutive objects are the same color or if a tank does not have sufficient capacity to fully paint an object.

The variant of FIGS. 6 and 7 illustrates a solution halfway between the two preceding ones, insofar as it comprises only two reservoirs (or at least a pair of such reservoirs) and means for rinsing and drying. The two reservoirs 22 are similar to those of the variant of FIGS. 4 and 5. They therefore each comprise first complementary connection means 29ai, 29a2 and second complementary connection means 34a, 34b each comprising two connector elements. The automaton is provided with second connection means similar to those of the variant of FIGS. 4 and 5. The two tanks are designed to be "hooked" to respective receivers, each comprising first connection means 28a _i , 28a2 mentioned above, capable of to cooperate with said first complementary connection means provided on the tanks. These first connection means also each comprise two connector elements.

The installation comprises, as in the case of FIG. 1, distribution circuits for coating product P1, P2, P3, a distribution circuit for cleaning product N, a circuit for evacuating waste D and a circuit d compressed air supply A. The reservoirs are supplied sequentially and selectively by means of a manifold-distributor 40 comprising two outlets 41a, 41b connected by controlled valves 42 to the first connection means and a certain number of inputs, including three inputs 43 ₁ , 43 ₂ , 43 ₃ connected by controlled valves 44 to the circuits P1, P2, P3. It further comprises an inlet 45 connected by a controlled valve 46 to the cleaning product distribution circuit N and an inlet 47 connected by a controlled valve 48 to the compressed air supply circuit A.

For each of the two tank receivers, the two connector elements of the first connection means are connected for one (28a2) to an outlet 41a or 41b of the manifold and for the other (28ai) to the evacuation circuit of waste D by a controlled valve 50 and to the air supply circuit A, by a controlled valve 52. The manifold-distributor 40 further comprises another outlet 54 connected by a controlled valve 56 to the waste discharge circuit D For each tank receiver, the connector element (28a2) of said first connection means which is connected to the outlet of the manifold-distributor is at a level lower than that of the other connector element (28ai) connected to the circuit. waste outlet D and air supply circuit A.

Each tank receiver can be provided with guides 60 facilitating the approach and the correct positioning of the tank in the case where the automaton does not have the required positioning precision. Such guides can be provided both in the vicinity of the reserovir supports and on the machine itself. Of course, such guides can be adapted to installations in accordance with Figures 1 to 5. The operation of the variant of Figures 6 and 7 is as follows.

When the automaton has finished painting an object, it comes to "hang up" one of the reservoirs 22 at one of the two locations provided for this purpose. He can then take the second tank before pivoting again to paint the next object. During this time, the collector-distributor 40 proceeds to a cleaning cycle, and to filling the previous tank. For this, the excess paint in this tank is first reinjected into the circuit P1, P2 or P3 of the corresponding color, by opening the corresponding valves 52, 42 and a valve 44. The reservoir is then sprayed by injection of cleaning product through the valve 46, the manifold-distributor and the same valve 42, the corresponding valve 50 being open and the corresponding valve 52 closed. After a drying phase of the reservoir, by circulation of air, by closing the valve 46 and opening the valve 48, the latter is placed in communication with the circuit of the new paint, by means of from one of the valves 44 and from the distributor 40, until a little excess paint is discharged into the circuit D. After the valves 42-44-50 are closed, the reservoir is then ready to be new used. The cycle ends with cleaning and drying of the manifold itself.

Although the examples of implementation of the invention have been described in the case of spraying, electrostatic or not, of liquid products such as paints, it goes without saying that it also applies to pulverulent products, for example, that powder paints. It suffices for this that the mobile intermediate storage tank (s) as well as the means of transport, projection, cleaning, recovery, etc., are adapted, in a manner known per se, by the specialists in the projection of powder, to powdery products. Thus, for example, it suffices to replace the pressurization of the reservoir by a fluidization of the powder using an air supply through a porous bottom, cleaning using a solvent with a blowing with compressed air, self-sealing ball connections by elastic sleeve valves also known, the waste receptacle by an extractor hood fitted with a separating filter, etc.

In the foregoing, almost exclusively reference has been made to changes in the color of the coating, but obviously these changes may as well relate to the nature of the product constituting the coating.

Of course, the invention is not limited to the variants described above. In particular, in the case where the paint projector is of relatively simple structure (air projector) it is perfectly possible to combine this projector or only part of it with the tank. In this case, said second complementary connection means of each reservoir comprise a connector element capable of cooperating with a connector element of the automaton in communication with a source of compressed air while the reservoir itself carries a specific projector. in communication with the interior of the tank.

Claims (20)

1. An installation for spraying coating products comprising at least robot of the multi-axis type, bearing a mobile product sprayer (20) facing a conveyor bearing objects to be coated, different coating product distribution circuits (P1-P3) being provided with respective like first connecting means (28a) which are arranged together at a fixed station in a zone of activity of said robot, characterised in that said robot carries a coating product tank (22), at least during each spraying phase, connected to supply said sprayer, and that said tank communicates with or is provided with first complementary connecting means (29a) capable of co-operating with said first connecting means of any one of the coating product distribution circuits.

2. An installation according to claim 1 characterised in that said coating product tank (22) is a single tank fixed to said robot and that it is disposed in the vincinity of said sprayer (20).

3. An installation according to claim 2 characterised in that it comprises a cleaning product distribution circuit (N) comprising means (28b) for connection to said tank, which are disposed in said zone of activity of said robot.

4. An installation according to claim 2 or claim 3 characterised in that it further comprises a waste evacuation circuit (D) comprising means (28c) for connection to said tank, which are disposed in said zone of activity of said robot.

5. An installation according to one of claims 2 to 4 characterised in that it comprises a waste recovery receptacle (30) which is disposed in said zone of activity of said robot and which is capable of receiving a product rejected by said sprayer.

6. An installation according to claim 1 characterised in that it comprises at least as many coating product tanks (22₁-22₃) as said distribution circuits (P1-P3) and that said robot comprises second connecting means capable of co-operating with second complementary connecting means (34a, 34b) provided on each tank.

7. An installation according to claim 6 characterised in that said first connecting means comprise two connector elements (28a_i, 28a₂) which are spaced by a predetermined distance on respective sides of a restriction (35) connected in series in the corresponding coating product supply circuit, said circuit being of the type involving continuous circulation, and that for each tank said first complementary connecting means comprise two other connector elements (29a_i, 29a₂) which are spaced by the same distance along said tank.

8. An installation according to claim 7 characterised in that the two connector elements (28ai, 28a₂) of any circuit are disposed at different levels, the connector (28ai) disposed at the higher level being downstream of the other connector element (28a₂) with respect to the direction of flow of said coating product in the corresponding distribution circuit.

9. An installation according to claim 7 or claim 8 characterised in that, for each coating product distribution circuit, the connector element (28a_i) which is disposed downstream of the other connector element with respect to the direction of flow of said coating product is connected to said distribution circuit by way of a controlled three-way valve (36) of which an outlet communicates with a discharge circuit (37).

10. An installation according to claim 9 characterised in that said discharge circuit (37) is common to all said three-way valves (36) which are associated with the different coating product distribution circuits.

11. An installation according to claim 1 characterised in that it comprises at least two tanks (22), that said robot comprises second connecting means capable of co-operating with second complementary connecting means (34a, 34b) provided on each tank and that a distributor manifold (40) is connected by way of an assembly of controlled valves on the one hand to said coating product distribution circuits (P1, P2, P3), to a cleaning product distribution circuit (N), to a waste evacuation conduit (D) and to a compressed air supply circuit, and on the other hand, to two tank vessels each comprising said first connecting means capable of co-operating with first complementary connecting means provided on each of the two tanks.

12. An installation according to claim 11 characterised in that, for each of said tank vessels, the first connecting means comprise two connector elements (28ai, 28a₂) spaced by a predetermined distance and respectively connected by way of controlled valves in respect of one (28a₂) to an output of said distributor manifold (40) and in respect of the other (28ai) to said waste evacuation circuit (D) and to said air supply circuit (A) and that, for each tank, said first complementary connecting means comprise two connector elements (29a_i, 29a₂) which are spaced by the same predetermined distance.

13. An installation according to claim 12 characterised in that said distributor manifold (40) comprises inlets (43) respectively connected by way of controlled valves to the different coating product distribution circuits, an inlet (45) connected by way of a controlled valve to said cleaning product distribution circuit, an inlet (47) connected by way of a controlled valve to said air supply circuit (A) and an outlet (54) connected by way of a controlled valve to said waste evacuation circuit (D).

14. An installation according to one of the preceding claims characterised in that guides (60) are disposed around each of said first connecting means.

15. An installation according to claim 12 characterised in that the connector element (28a₂) of said first connecting means which is connected to the outlet of said distributor manifold is at a lower level than the other connector element (28ai) which is connected to said waste evacuation circuit and to said air supply circuit.

16. An installation according to claim 6 or claim 11 characterised in that the second complementary connecting means (34a, 34b) of each tank comprise two connector elements which are spaced from each other by a predetermined distance, one of the connector elements being capable of co-operating with a connector element of said robot in communication with a compressed air source and the other connecting element being capable of co-operating with a connector element of said robot in communication with said sprayer, which are spaced from each other by the same predetermined distance.

17. An installation according to claim 6 or claim 11 characterised in that said second complementary connecting means of each tank comprise a connector element capable of co-operating with a connector element of said robot in communication with a compressed air source for actuation of the sprayer and that said tank bears a specific sprayer.

18. An installation according to one of the preceding claims characterised in that said robot is connected to an adjustable high-tension source (24) capable of being reset to zero outside the periods of spraying by said sprayer.

19. An installation according to claim 18 characterised in that said coating product distribution circuits are filled with water-based paint of different colours.

20. An installation according to one of the preceding claims characterised in that the or each tank (22) contains a piston or a deformable diaphragm dividing the interior of the tank into two chambers, one of the chambers accommodating said coating product and the other chamber being intended to be connected to a compressed air source.

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